WO2001006022A1 - Method for making a continuous steel strip - Google Patents

Method for making a continuous steel strip Download PDF

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Publication number
WO2001006022A1
WO2001006022A1 PCT/BE2000/000071 BE0000071W WO0106022A1 WO 2001006022 A1 WO2001006022 A1 WO 2001006022A1 BE 0000071 W BE0000071 W BE 0000071W WO 0106022 A1 WO0106022 A1 WO 0106022A1
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WO
WIPO (PCT)
Prior art keywords
temperature
aqueous bath
steel strip
bath
cooling
Prior art date
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PCT/BE2000/000071
Other languages
French (fr)
Inventor
Vittorino Tusset
Pierre Simon
Jean Crahay
Mario Economopoulos
Original Assignee
Centre De Recherches Metallurgiques
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Centre De Recherches Metallurgiques filed Critical Centre De Recherches Metallurgiques
Priority to EP00943485A priority Critical patent/EP1204770B8/en
Priority to AU57978/00A priority patent/AU5797800A/en
Priority to AT00943485T priority patent/ATE248234T1/en
Priority to DE60004865T priority patent/DE60004865T2/en
Publication of WO2001006022A1 publication Critical patent/WO2001006022A1/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/60—Aqueous agents
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • C21D9/54—Furnaces for treating strips or wire
    • C21D9/56—Continuous furnaces for strip or wire
    • C21D9/573—Continuous furnaces for strip or wire with cooling

Definitions

  • the present invention relates to a method for manufacturing a continuous steel strip, and more particularly to a method for cooling a steel strip in a continuous annealing and / or coating line.
  • a boiling water quenching process is already known, to which the steel strip is subjected as soon as it leaves a continuous annealing furnace.
  • This known process is self-regulating, since the aqueous bath is constantly maintained at boiling point by the steel strip which enters it at a temperature of the order of 700 ° C to 850 ° C.
  • a steel strip thus treated has a very good surface condition.
  • its flatness is excellent, provided, however, that the steel strip has, on leaving the quench bath, a temperature higher than the transition temperature of cooling.
  • the cooling transition temperature is the temperature of the strip for which the cooling of the strip by the quench bath passes from a heat exchange through a continuous vapor film to a heat exchange through a discontinuous layer of vapor bubbles.
  • the cooling transition temperature is approximately 320 ° C.
  • the steel strip leaves the quench bath at a temperature of the order of 350 ° C; it is then either subjected to an overaging treatment without intermediate cooling, or cooled to room temperature, that is to say up to less than 100 ° C by other suitable means.
  • a drawback of this process is that its cooling rate is limited, for example of the order of 50 ° C / s to 60 ° C / s for a steel strip 0.8 mm thick. In addition, it does not make it possible, without an auxiliary cooling system, to cool the steel strip to less than 100 ° C. (full quench) while retaining a satisfactory flatness of the strip.
  • Another system is also known, working by spraying with water at about 80 ° C., which makes it possible to cool the steel strip to less than 100 ° C. and to increase the cooling rate.
  • This system is however not compatible with quenching with boiling water, in particular because of the markedly different temperatures imposed by the two methods.
  • the present invention provides a method of manufacturing a steel strip continuously, which makes it possible on the one hand to lower the final temperature for cooling the strip and on the other hand to increase its cooling rate, without any degradation in flatness.
  • a process for manufacturing a steel strip continuously in which the steel strip is immersed, at a temperature between 700 ° C and 850 ° C, in an aqueous bath maintained at a temperature above room temperature, is characterized in that at least one surfactant capable of lowering the surface tension of said aqueous bath by at least 20 dynes / cm is added to said aqueous bath, in that the said surfactant is added in a proportion of between 0.5 g / 1 and 50 g / 1, and in this way that the surface tension of said aqueous bath is lowered to a value less than 30 dynes / cm.
  • surfactants capable of withstanding temperatures above 110 ° C., and preferably also at pressures of at least 2 bar.
  • an aqueous bath consisting of a boiling water bath, known per se, which can have a depth of several meters.
  • a boiling water bath known per se, which can have a depth of several meters.
  • the cooling transition temperature can be lowered to around 125 ° C.
  • an aqueous bath is used at a temperature of 50 ° C to 90 ° C.
  • a lowering of the temperature of the aqueous bath compared to a quenching with boiling water, has the effect of increasing the heat transfer coefficient between the steel strip and the aqueous bath.
  • the cooling rates obtained in a liquid bath, the temperature is between 50 and 90 ° C are also much higher than those obtained in cooling systems using only gas flows.
  • the cooling rate goes from about 50 to 60 ° C / s for cooling with boiling water, to about 150 to 200 ° C / s for cooling with water to 80 ° C, in the case of a steel strip 0.8 mm thick.
  • this lowering of the temperature of the aqueous bath also influences the transition temperature of the cooling.
  • this cooling transition temperature is 550 ° C in a water bath at 70 ° C; it can be lowered to around 300 ° C by an appropriate addition of at least one of the above-mentioned surfactants.
  • At least one organic acid chosen from acetic acid, benzoic acid and formic acid, is added to said aqueous bath, at a concentration C, expressed in g / l, given by the formula :
  • T ba ⁇ n is the temperature of the quench bath Ci is a specific coefficient of the acid used, which is 0.09 for acetic acid 0.12 for benzoic acid 0.04 for formic acid.
  • This variant is particularly advantageous for the manufacture of non-oxidized steel strips, intended in particular to be galvanized directly.
  • the surface-active substances added to the aqueous bath must also resist the aforementioned organic acids.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • Coating With Molten Metal (AREA)
  • Control Of Heat Treatment Processes (AREA)

Abstract

The invention concerns a method for making a continuous steel strip, which consists in: dipping the steel strip, at a temperature ranging between 700 °C and 850 °C, in an aqueous bath maintained at a temperature above room temperature; adding to the aqueous bath at least a surfactant capable of lowering the surface tension of said aqueous bath by at least 20 dynes/cm; adding said surfactant in a proportion ranging between 0.5 g/l and 50 g/l and thereby lowering the aqueous bath surface tension to a value less than 30 dynes/cm. The temperature of the bath can be substantially its boiling point. Preferably, surfactants capable of resisting to temperatures above 110 °C, to pressure levels of at least 2 bar, and optionally to organic acids added to the bath are used, when making a non-oxidised strip.

Description

C.2697 - Procédé de fabrication d'une bande d'acier en continu.C.2697 - Continuous method of manufacturing a steel strip.
Domaine techniqueTechnical area
La présente invention concerne un procédé de fabrication d'une bande d'acier en continu, et plus particulièrement un procédé de refroidissement d'une bande d'acier dans une ligne de recuit continu et/ou de revêtement.The present invention relates to a method for manufacturing a continuous steel strip, and more particularly to a method for cooling a steel strip in a continuous annealing and / or coating line.
Etat de la techniqueState of the art
Dans le domaine technique de la fabrication d'une bande d'acier en continu, on connaît déjà un procédé de trempe à l'eau bouillante, auquel la bande d'acier est soumise dès sa sortie d'un four de recuit continu. Ce procédé connu est auto-régulé, puisque le bain aqueux est en permanence maintenu à l'ébullition par la bande d'acier qui y pénètre à une température de l'ordre de 700°C à 850°C. Une bande d'acier ainsi traitée présente un très bon état de surface. En outre, sa planéité est excellente, à la condition toutefois que la bande d'acier présente, à sa sortie du bain de trempe, une température supérieure à la température de transition du refroidissement.In the technical field of manufacturing a continuous steel strip, a boiling water quenching process is already known, to which the steel strip is subjected as soon as it leaves a continuous annealing furnace. This known process is self-regulating, since the aqueous bath is constantly maintained at boiling point by the steel strip which enters it at a temperature of the order of 700 ° C to 850 ° C. A steel strip thus treated has a very good surface condition. In addition, its flatness is excellent, provided, however, that the steel strip has, on leaving the quench bath, a temperature higher than the transition temperature of cooling.
Au sens de la présente demande, la température de transition du refroidissement est la température de la bande pour laquelle le refroidissement de la bande par le bain de trempe passe d'un échange thermique à travers un film de vapeur continu à un échange thermique à travers une couche discontinue de bulles de vapeur.Within the meaning of the present application, the cooling transition temperature is the temperature of the strip for which the cooling of the strip by the quench bath passes from a heat exchange through a continuous vapor film to a heat exchange through a discontinuous layer of vapor bubbles.
Dans les conditions usuelles de cette trempe à l'eau bouillante et pour une bande d'acier, la température de transition du refroidissement est d'environ 320°C.Under the usual conditions of this quenching with boiling water and for a steel strip, the cooling transition temperature is approximately 320 ° C.
Typiquement, la bande d'acier quitte le bain de trempe à une température de l'ordre de 350°C; elle est alors soit soumise à un traitement ultérieur de survieillissement sans refroidissement intermédiaire, soit refroidie jusqu'à la température ambiante, c'est-à-dire jusqu'à moins de 100°C par d'autres moyens appropriés.Typically, the steel strip leaves the quench bath at a temperature of the order of 350 ° C; it is then either subjected to an overaging treatment without intermediate cooling, or cooled to room temperature, that is to say up to less than 100 ° C by other suitable means.
Un inconvénient de ce procédé est que sa vitesse de refroidissement est limitée, par exemple de l'ordre de 50°C/s à 60°C/s pour une bande d'acier de 0,8 mm d'épaisseur. En outre, il ne permet pas d'effectuer, sans système de refroidissement auxiliaire, un refroidissement de la bande d'acier jusqu'à moins de 100°C (full quench) tout en conservant une planéité satisfaisante de la bande.A drawback of this process is that its cooling rate is limited, for example of the order of 50 ° C / s to 60 ° C / s for a steel strip 0.8 mm thick. In addition, it does not make it possible, without an auxiliary cooling system, to cool the steel strip to less than 100 ° C. (full quench) while retaining a satisfactory flatness of the strip.
Divers systèmes, notamment par jets d'eau et/ou de brouillard, ont été proposés pour poursuivre le refroidissement de la bande sans nuire à sa planéité. Il s'agit cependant en général de systèmes coûteux, bruyants et difficiles à conduire, qui n'ont pas connu, à ce jour, de réelle application industrielle.Various systems, notably by water jets and / or mist, have been proposed to continue cooling the strip without affecting its flatness. However, these are generally expensive, noisy and difficult to drive systems which have not, to date, had any real industrial application.
Il existe aussi des procédés de refroidissement basés sur l'utilisation de flux de gaz ou de rouleaux refroidis; ces procédés sont très onéreux à mettre en oeuvre et ne fournissent d'ailleurs pas les vitesses de refroidissement très élevées, exigées notamment par les aciers de résistance ; ces procédés entraînent en outre certains problèmes de planéité de la bande.There are also cooling methods based on the use of gas streams or cooled rollers; these methods are very expensive to implement and do not, moreover, provide the very high cooling rates, required in particular by resistance steels; these methods also lead to certain problems of flatness of the strip.
On connaît par ailleurs un autre système, travaillant par aspersion avec une eau à environ 80°C, qui permet de refroidir la bande d'acier jusqu'à moins de 100°C et d'augmenter la vitesse de refroidissement. Ce système n'est cependant pas compatible avec une trempe à l'eau bouillante, notamment à cause des températures nettement différentes imposées par les deux procédés.Another system is also known, working by spraying with water at about 80 ° C., which makes it possible to cool the steel strip to less than 100 ° C. and to increase the cooling rate. This system is however not compatible with quenching with boiling water, in particular because of the markedly different temperatures imposed by the two methods.
Présentation de l'inventionPresentation of the invention
Il existe actuellement une demande pour des bandes en aciers de résistance, présentant néanmoins également une bonne planéité. En raison des inconvénients et des limitations des procédés rappelés plus haut, ceux-ci ne permettent pas de fabriquer des bandes d'acier de cette qualité. Partant de cet état de la technique, la présente invention propose un procédé de fabrication d'une bande d'acier en continu, qui permet d'une part d'abaisser la température finale de refroidissement de la bande et d'autre part d'augmenter sa vitesse de refroidissement, sans aucune dégradation de la planéité.There is currently a demand for strips of resistance steels, which nevertheless also exhibit good flatness. Due to the drawbacks and limitations of the processes mentioned above, these do not make it possible to manufacture steel strips of this quality. Starting from this state of the art, the present invention provides a method of manufacturing a steel strip continuously, which makes it possible on the one hand to lower the final temperature for cooling the strip and on the other hand to increase its cooling rate, without any degradation in flatness.
Conformément à l'invention, un procédé de fabrication d'une bande d'acier en continu, dans lequel on plonge la bande d'acier, à une température comprise entre 700°C et 850°C, dans un bain aqueux maintenu à une température supérieure à la température ambiante, est caractérisé en ce que l'on ajoute audit bain aqueux au moins une substance tensio- active capable d'abaisser la tension superficielle dudit bain aqueux d'au moins 20 dynes/cm, en ce que l'on ajoute ladite substance tensio-active en une proportion comprise entre 0,5 g/1 et 50 g/1, et en ce que l'on abaisse ainsi la tension superficielle dudit bain aqueux à une valeur inférieure à 30 dynes/cm.According to the invention, a process for manufacturing a steel strip continuously, in which the steel strip is immersed, at a temperature between 700 ° C and 850 ° C, in an aqueous bath maintained at a temperature above room temperature, is characterized in that at least one surfactant capable of lowering the surface tension of said aqueous bath by at least 20 dynes / cm is added to said aqueous bath, in that the said surfactant is added in a proportion of between 0.5 g / 1 and 50 g / 1, and in this way that the surface tension of said aqueous bath is lowered to a value less than 30 dynes / cm.
Suivant l'invention, on utilise avantageusement des substances tensio-actives capables de résister à des températures supérieures à 110°C, et de préférence aussi à des pressions d'au moins 2 bar.According to the invention, use is advantageously made of surfactants capable of withstanding temperatures above 110 ° C., and preferably also at pressures of at least 2 bar.
Suivant une première mise en œuvre, on utilise un bain aqueux constitué par un bain d'eau bouillante, connu en soi, qui peut présenter une profondeur de plusieurs mètres. L'addition de telles substances tensio-actives à un bain d'eau bouillante, conformément à l'invention, permet d'abaisser la température de transition du refroidissement, et donc de prolonger le refroidissement de la bande d'acier en dessous de la température précitée de 320°C. Selon la substance tensio-active utilisée, la température de transition du refroidissement peut ainsi être abaissée jusqu'à environ 125°C. Ces valeurs correspondent à une bande de 0,8 mm d'épaisseur; elles peuvent varier légèrement dans la gamme des épaisseurs de bande concernées.According to a first implementation, an aqueous bath is used consisting of a boiling water bath, known per se, which can have a depth of several meters. The addition of such surface-active substances to a boiling water bath, in accordance with the invention, makes it possible to lower the transition temperature of the cooling, and therefore to prolong the cooling of the steel strip below the above-mentioned temperature of 320 ° C. Depending on the surfactant used, the cooling transition temperature can be lowered to around 125 ° C. These values correspond to a strip 0.8 mm thick; they may vary slightly in the range of strip thicknesses concerned.
Suivant une autre mise en œuvre particulière, on utilise un bain aqueux à une température de 50°C à 90°C. Un tel abaissement de la température du bain aqueux, par rapport à une trempe à l'eau bouillante, a pour effet d'augmenter le coefficient de transfert de chaleur entre la bande d'acier et le bain aqueux. Il en résulte une augmentation de la vitesse de refroidissement de la bande d'acier, ce qui est favorable pour la fabrication de bandes en acier de résistance. Les vitesses de refroidissement obtenues dans un bain liquide dont la température est comprise entre 50 et 90°C sont aussi beaucoup plus élevées que celles obtenues dans les systèmes de refroidissement utilisant uniquement des flux de gaz.According to another particular implementation, an aqueous bath is used at a temperature of 50 ° C to 90 ° C. Such a lowering of the temperature of the aqueous bath, compared to a quenching with boiling water, has the effect of increasing the heat transfer coefficient between the steel strip and the aqueous bath. This results in an increase in the cooling rate of the steel strip, which is favorable for the manufacture of resistance steel strips. The cooling rates obtained in a liquid bath, the temperature is between 50 and 90 ° C are also much higher than those obtained in cooling systems using only gas flows.
A titre d'exemple, la vitesse de refroidissement passe d'environ 50 à 60°C/s pour un refroidissement à l'eau bouillante, à environ 150 à 200°C/s pour un refroidissement par de l'eau à 80°C, dans le cas d'une bande d'acier de 0,8 mm d'épaisseur.For example, the cooling rate goes from about 50 to 60 ° C / s for cooling with boiling water, to about 150 to 200 ° C / s for cooling with water to 80 ° C, in the case of a steel strip 0.8 mm thick.
Parallèlement, cet abaissement de la température du bain aqueux influence également la température de transition du refroidissement. En particulier, pour une bande d'acier, cette température de transition du refroidissement est de 550°C dans un bain d'eau à 70°C; elle peut être abaissée jusqu'à environ 300°C par une addition appropriée d'au moins une des substances tensio-actives précitées.At the same time, this lowering of the temperature of the aqueous bath also influences the transition temperature of the cooling. In particular, for a steel strip, this cooling transition temperature is 550 ° C in a water bath at 70 ° C; it can be lowered to around 300 ° C by an appropriate addition of at least one of the above-mentioned surfactants.
Il est cependant impératif que la bande quitte le bain de trempe à une température supérieure à cette température de transition pour conserver sa planéité.However, it is imperative that the strip leaves the quenching bath at a temperature above this transition temperature to maintain its flatness.
Dans ces conditions, lorsque la température de transition du refroidissement est trop nettement supérieure à la température de 100°C - cas d'un bain aqueux à 70-80°C avec ou sans addition de substances tensio-actives - on peut alors, suivant une variante de l'invention, poursuivre le refroidissement de la bande d'acier jusqu'à moins de 100°C (full quench), sans perte de planéité, en appliquant un refroidissement par aspersion avec de l'eau à 70-80°C. Cette eau peut ensuite être renvoyée dans le bain aqueux.Under these conditions, when the cooling transition temperature is too markedly higher than the temperature of 100 ° C. - in the case of an aqueous bath at 70-80 ° C. with or without the addition of surfactants - it is then possible, according to a variant of the invention, continue cooling the steel strip to less than 100 ° C (full quench), without loss of flatness, by applying spray cooling with water at 70-80 ° vs. This water can then be returned to the aqueous bath.
Suivant encore une autre caractéristique particulière, on ajoute audit bain aqueux au moins un acide organique, choisi parmi l'acide acétique, l'acide benzoïque et l'acide formique, en une concentration C, exprimée en g/l, donnée par la formule:According to yet another particular characteristic, at least one organic acid, chosen from acetic acid, benzoic acid and formic acid, is added to said aqueous bath, at a concentration C, expressed in g / l, given by the formula :
C = 80 + 10 D [Ci (150 - Tbaιn)]C = 80 + 10 D [Ci (150 - T baιn )]
dans laquelle: C est la concentration minimale de l'acide utiliséin which: C is the minimum concentration of acid used
Tbaιn est la température du bain de trempe Ci est un coefficient spécifique de l'acide utilisé, qui vaut 0,09 pour l'acide acétique 0,12 pour l'acide benzoïque 0,04 pour l'acide formique.T baιn is the temperature of the quench bath Ci is a specific coefficient of the acid used, which is 0.09 for acetic acid 0.12 for benzoic acid 0.04 for formic acid.
Cette variante s'avère particulièrement avantageuse pour la fabrication de bandes d'acier non oxydées, destinées notamment à être galvanisées directement.This variant is particularly advantageous for the manufacture of non-oxidized steel strips, intended in particular to be galvanized directly.
Dans le cas de cette variante particulière, les substances tensio-actives ajoutées au bain aqueux doivent en outre résister aux acides organiques précités.In the case of this particular variant, the surface-active substances added to the aqueous bath must also resist the aforementioned organic acids.
A titre d'exemples de substances tensio-actives présentant les propriétés requises de résistance à des températures supérieures à 110°C, à des pressions d'au moins 2 bar ainsi qu'aux acides organiques précités, on peut mentionner les composés suivants, sans que cette énumération soit limitative:As examples of surfactants having the required properties of resistance to temperatures above 110 ° C., to pressures of at least 2 bar and to the abovementioned organic acids, the following compounds may be mentioned, without that this list is exhaustive:
- tristéarate de sorbitan- sorbitan tristearate
- trioléate de sorbitan- sorbitan trioleate
- isostéarate de sorbitan- sorbitan isostearate
- monostéarate de sorbitan- sorbitan monostearate
- monolaurate de sorbitan- sorbitan monolaurate
- monostéarate de pentaérythritol- pentaerythritol monostearate
- monooléate de pentaérythritol- pentaerythritol monooleate
- dioléate de propylène glycol.- propylene glycol dioleate.
Il va de soi que ces composés peuvent être présents, en concentrations variables, dans les substances tensio-actives utilisées conformément à l'invention. It goes without saying that these compounds can be present, in varying concentrations, in the surface-active substances used in accordance with the invention.

Claims

Revendications claims
1. Procédé de fabrication d'une bande d'acier en continu, dans lequel on plonge la bande d'acier, à une température comprise entre 700°C et 850°C, dans un bain aqueux maintenu à une température supérieure à la température ambiante, caractérisé en ce que l'on ajoute audit bain aqueux au moins une substance tensio- active capable d'abaisser la tension superficielle dudit bain aqueux d'au moins 20 dynes/cm, en ce que l'on ajoute ladite substance tensio-active en une proportion comprise entre 0,5 g/l et 50 g/l, et en ce que l'on abaisse ainsi la tension superficielle dudit bain aqueux à une valeur inférieure à 30 dynes/cm.1. A method of manufacturing a steel strip continuously, in which the steel strip is immersed, at a temperature between 700 ° C and 850 ° C, in an aqueous bath maintained at a temperature above the temperature ambient, characterized in that at least one surface-active substance capable of lowering the surface tension of said aqueous bath is added to said aqueous bath by at least 20 dynes / cm, in that said surface-active substance is added active in a proportion of between 0.5 g / l and 50 g / l, and in that the surface tension of said aqueous bath is thus lowered to a value less than 30 dynes / cm.
2. Procédé suivant la revendication 1 , caractérisé en ce que l'on utilise des substances tensio-actives capables de résister à des températures supérieures à 110°C.2. Method according to claim 1, characterized in that surfactants capable of withstanding temperatures above 110 ° C are used.
3. Procédé suivant l'une ou l'autre des revendications 1 et 2, caractérisé en ce que l'on utilise des substances tensio-actives capables de résister à des pressions d'au moins 2 bar.3. Method according to either of Claims 1 and 2, characterized in that surface-active substances capable of withstanding pressures of at least 2 bar are used.
4. Procédé suivant l'une ou l'autre des revendications 1 à 3, caractérisé en ce que ledit bain aqueux se trouve sensiblement à sa température d'ébullition.4. Method according to either of claims 1 to 3, characterized in that said aqueous bath is substantially at its boiling temperature.
5. Procédé suivant l'une ou l'autre des revendications 1 à 3, caractérisé en ce que ledit bain aqueux se trouve à une température de 50°C à 90CC.5. Method according to either of claims 1 to 3, characterized in that said aqueous bath is at a temperature of 50 ° C to 90 C C.
6. Procédé suivant la revendication 5, caractérisé en ce que la bande d'acier sort dudit bain aqueux à une température supérieure à sa température de transition du refroidissement et en ce qu'elle est soumise à un refroidissement complémentaire par aspersion avec de l'eau à 50°C-90°C.6. Method according to claim 5, characterized in that the steel strip leaves said aqueous bath at a temperature above its transition temperature of cooling and in that it is subjected to additional cooling by spraying with water at 50 ° C-90 ° C.
7. Procédé suivant l'une ou l'autre des revendications 1 à 6, caractérisé en ce que l'on ajoute audit bain aqueux au moins un acide organique, choisi parmi l'acide acétique, l'acide benzoïque et l'acide formique, en une concentration C, exprimée en g/l, donnée par la formule:7. Method according to either of Claims 1 to 6, characterized in that at least one organic acid, chosen from acetic acid, benzoic acid and formic acid, is added to said aqueous bath , at a concentration C, expressed in g / l, given by the formula:
C = 80 + 10 D [Ci (150 - Tbaιn)]C = 80 + 10 D [Ci (150 - T baιn )]
dans laquelle: C est la concentration minimale de l'acide utiliséin which: C is the minimum concentration of acid used
Tbaιn est la température du bain de trempe Ci est un coefficient spécifique de l'acide utilisé.T baιn is the temperature of the quench bath Ci is a specific coefficient of the acid used.
Procédé suivant la revendication 7, caractérisé en ce que lesdites substances tensio-actives sont capables de résister auxdits acides organiques. Method according to Claim 7, characterized in that the said surface-active substances are capable of resisting the said organic acids.
PCT/BE2000/000071 1999-07-19 2000-06-27 Method for making a continuous steel strip WO2001006022A1 (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
EP00943485A EP1204770B8 (en) 1999-07-19 2000-06-27 Method for making a continuous steel strip
AU57978/00A AU5797800A (en) 1999-07-19 2000-06-27 Method for making a continuous steel strip
AT00943485T ATE248234T1 (en) 1999-07-19 2000-06-27 CONTINUOUS PROCESS FOR PRODUCING A STEEL STRIP
DE60004865T DE60004865T2 (en) 1999-07-19 2000-06-27 CONTINUOUS METHOD FOR PRODUCING A STEEL STRIP

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BE9900492A BE1012789A3 (en) 1999-07-19 1999-07-19 Manufacturing method of steel strip continuous.
BE9900492 1999-07-19

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Publication number Priority date Publication date Assignee Title
EP1528109A1 (en) * 2003-10-28 2005-05-04 Mannesmannröhren-Werke AG Porcess for the heat treatment of medium carbon steels

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WO2008051973A1 (en) 2006-10-24 2008-05-02 Bradley Fixtures Corporation Capacitive sensing for washroom fixture

Citations (4)

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Publication number Priority date Publication date Assignee Title
FR858096A (en) * 1938-08-01 1940-11-16 Fruit Growers Exchange Ca Hardening process for steel and other alloys
DE2727744A1 (en) * 1976-06-23 1978-01-05 Centre Rech Metallurgique Continuous heat treatment of steel sheet - quenched in water contg. an organic acid to prevent oxidn. during quenching
JPS5858233A (en) * 1981-09-30 1983-04-06 Nippon Kokan Kk <Nkk> Non-oxidation hardening method for strip by organic acid
GB2150159A (en) * 1983-11-24 1985-06-26 Fire Out Systems Limited Cooling heated surfaces

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR858096A (en) * 1938-08-01 1940-11-16 Fruit Growers Exchange Ca Hardening process for steel and other alloys
DE2727744A1 (en) * 1976-06-23 1978-01-05 Centre Rech Metallurgique Continuous heat treatment of steel sheet - quenched in water contg. an organic acid to prevent oxidn. during quenching
JPS5858233A (en) * 1981-09-30 1983-04-06 Nippon Kokan Kk <Nkk> Non-oxidation hardening method for strip by organic acid
GB2150159A (en) * 1983-11-24 1985-06-26 Fire Out Systems Limited Cooling heated surfaces

Non-Patent Citations (1)

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Title
PATENT ABSTRACTS OF JAPAN vol. 007, no. 147 (C - 173) 28 June 1983 (1983-06-28) *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1528109A1 (en) * 2003-10-28 2005-05-04 Mannesmannröhren-Werke AG Porcess for the heat treatment of medium carbon steels

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BE1012789A3 (en) 2001-03-06
AU5797800A (en) 2001-02-05
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DE60004865D1 (en) 2003-10-02
EP1204770B8 (en) 2004-04-21

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